Effect of electrodeless glow discharge on polymers

The effects of gas plasma generated by electrodeless (inductive coupling) glow discharge on polymers were investigated as functions of gas pressure, discharge power, exposure time, and type of plasma gas. A remarkable similarity between the plasma susceptibilities of low molecular weight organic compounds and polymers was observed; i.e., polymers which have ether, carbonyl, ester, or carboxylic acid attached to a nonaromatic structure are very susceptible to plasma. The weight loss was proportional to the exposure time and exposed area. The discharge power and type of gas were found to have a great influence on both the rate of weight loss and the morphology of the exposed surface. The predominant effect of plasma on polymers was found to be degradation (manifested by weight loss). The crosslinking effect was found to be marginal with many polymers; however, significant crosslinking was observed with double bond-containing polymers. The crosslinking was examined by swelling the treated films. With copolymers of styrene–butadiene, 4-vinylpyridine–butadiene, methacrylic acid-butadiene, and acrylic acid–butadiene, the crosslinking was greatly dependent on the discharge power, the butadiene content of the copolymers, and the exposure time. Both degradation and crosslinking by gas plasma were generally limited to the exposed surface; however, the propagation of crosslinking in the direction of thickness was observed with copolymers of styrene–butadiene. The plasma of organic vapor also cause degradation of plasma-susceptible polymers, particularly at high wattage, although the deposition of polymer occurs simultaneously.     

Oxidation behavior of isoprene polymers and butadiene polymers

The oxidation behavior of cis-1,4-polyisoprene, emulsion polyisoprene, emulsion isoprene/styrene copolymers, and emulsion butadiene/styrene copolymers by heat aging or ultraviolet irradiation has been investigated from the change of gel fraction and molecular weight distribution. It was determined that the oxidation behavior of both isoprene and butadiene polymers is strongly dependent on the composition of the polymers as well as on the microstructure of the polymers. In the case of oxidation by heat aging, the probability ratio of chain scission to crosslinking of both isoprene and butadiene copolymers increases gradually with increasing styrene fraction. In the case of oxidation by ultraviolet irradiation, isoprene copolymers show a remarkable increase in the probability ratio of chain scission to crosslinking, whereas butadiene copolymers show substantially no change with increase in styrene fraction. It was also demonstrated that both isoprene and butadiene polymers show a greater tendency for crosslinking with oxidation by ultraviolet irradiation than with oxidation by heat aging.     

Some morphological aspects of AB crosslinked polymers

The structures of multicomponent species present in AB crosslinked polymers (ABCPs) formed by the random introduction of crosslinks of polymer B into an assembly of chains of polymer A are described for different extents of crosslinking. Microphase separation has been observed in solvent cast samples of ABCPs prepared by crosslinking poly(vinyl trichloroacetate) and a styrene copolymer (A-components) with polychloroprene (B-component). The morphologies of the polymers at low and high degrees of crosslinking are presented. Polychloroprene domain sizes have been determined for various crosslink lengths and crosslink densities. Domain sizes and their variation with molecular weight of the B-chains are discussed in terms of the structures of the multicomponent species present in the ABCPs and with theoretically predicted domain sizes in linear block copolymers. Distributions of domain sizes have been determined and compared with the molecular weight distributions of the B-chains.     

Synthesis of star-shaped polymers by coupling reaction between multifunctional core and terminal functionalized polymers

Star-shaped polymers that consist of well-defined polystyrene (PS) arms were successfully synthesized in high yield by coupling reaction between multifunctional core molecules and hydroxyl-terminated PS in the presence of 1, 3-dicyclohexylcarbodiimide and 4-(dimethylamino) pyridine at room temperature. Several systems were investigated: (1) Pyromellitic dianhydride (PMDA) and hydroxyl-terminated PS (PS-OH) with narrow molecular weight distribution, which was prepared by atom transfer radical polymerization (ATRP) of St with 2-hydroxyethyl bromoisobutylate (HEBiB) as initiator. (2) PMDA and PS-OH prepared by conventional free radical polymerization, with 2-mercaptoethanol as chain transfer agent. (3) Narrow molecular weight distributed alternating copolymer of maleic anhydride (MA) and styrene (St), which was obtained via reversible addition fragmentation chain transfer polymerization (RAFT) process, and PS-OH obtained by ATRP. The formation of star-shaped PSs was confirmed by proton nuclear magnetic resonance (¹H NMR) and gel permeation chromatography (GPC).     

Studies on the preparation of branched polymers from styrene and divinylbenzene

The self‐condensing vinyl polymerization of styrene and an inimer formed in situ by atom transfer radical addition from divinylbenzene and 2‐bromoisobutyl‐tert‐butyrate using atom transfer radical polymerization technique was studied. To study the polymerization mechanism and achieve high molecular weight polymer in a high polymer yield, the polymerization was carried out in bulk at 80°C. Proton nuclear magnetic resonance (¹H‐NMR) spectroscopy and gel permeation chromatography (GPC) coupled with multiangle laser light scattering (MALLS) were used to monitor the polymerization process and characterize the solid polymers. It is proved that the polymerization shows a “living” polymerization behavior and the crosslinking reaction has been restrained effectively due to the introduction of styrene. Polymers with high molecular weight (M_w.MALLS > 10⁵) can be prepared in high yield (near 80%). Comparison of the apparent molecular weights measured by GPC with the absolute values measured by MALLS indicates the existence of branched structures in the prepared polymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Architecture of nanostructured polymers by segregated domain crosslinking of block‐graft copolymer micelles

Polystyrene‐block‐polyisoprene (PS‐block‐PI; high 3,4‐structure) diblock copolymer was prepared by living anionic polymerization. For transfer into a reactive intermediate, the hydroxylation of the double bonds of PI block was achieved by hydroboration, followed by oxidation. Esterification of the hydroxy‐derivative with stearoyl chloride or decanoyl chloride resulted in block‐graft copolymers composed of PS (flexible chain)‐grafted long alkane (stretched chains). After partial chloromethylation of PS block copolymer, photofunctional N,N‐diethyldithiocarbamate (DC) groups were introduced into such pendant sites by reaction with the corresponding sodium salt. We studied the self‐assemblies of photofunctional block‐graft copolymers in a selective solvent, such as heptane, and constructed nanostructured polymers by crosslinking PS cores under UV irradiation. © 2001 Society of Chemical Industry     

Branching process of the grafting reaction between two reactive polymers

Graft coupling between two reactive polymers can lead to the formation of compatibilized blends. There is a need to control the extent of graft coupling if the grafting system is capable of gelation, not just for the control of phase size and morphology, which depend on the amount and structures of graft copolymers in a ternary blend. In this paper, we give a thorough analysis of the molecular characteristics of the grafting system of two reactive polymers each having a large number of reactive groups. A kinetic approach is employed to quantify the molecular characteristics: concentration of individual species, molecular-weight averages and gel point. It is found that the percentage conversions of the reactive polymers to copolymers are quite limited in order to avoid a weight-average molecular weight of the system that is too high. The presence of a high-molecular-weight tail in the polydisperse reactive polymers further limits the extent of the grafting reaction, an undesirable factor in such a grafting system.     

LC multiblock copolymers containing polysulfone segments. II. Material properties

The synthesis of multiblock copolymers containing liquid crystalline, semi-aromatic polyester segments of poly(ethylene terephthalate-co-oxybenzoate), and polysulfone segments with different segment molecular weights was recently described. Such block copolymers should make it possible to combine properties of the base homopolymers, e.g., the high strength of liquid crystalline polymers (LCP) with the high thermostability of polysulfone (PSU). Investigations of melt rheology and relaxation behavior discussed here demonstrated that the properties of the block copolymers are intermediate between those of the homopolymers and can be tailored by using PSU and LCP segments of suitable molecular weight. The high melt viscosity of PSU is lowered by block copolymer formation, allowing good processability by injection molding. The material properties of the resulting samples are characterized by a combination of PSU thermostability and improved strength. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 619–630, 1997     

Synthesis and properties of polyvinyl chloride-co-trimethylolpropane monoallylether)

A thermally stable, high molecular weight copolymer of vinyl chloride and trimethylolpropane monoallylether (PVC-co-TMPME) has been synthesized via the suspension polymerization process. Proton nuclear magnetic resonance (NMR) characterization of the copolymer shows the presence of TMPME in the saturated form, indicative of the TMPME reaction. Characterization by differential scanning calorimetry (DSC) shows that the glass transition temperature of the TMPME copolymer is similar to that of the homopolymer, and to that of a 5% vinyl acetate (PVC-co-VA) copolymer. Characterization of plasticized polymers by dynamic mechanical analysis (DMA) shows that both PVC-co-TMPME and PVC-co-VA have lower modulae than the corresponding homopolymer, as well as lower distortion temperatures, as shown by creep compliance master curves. These data indicate that PVC-co-TMPME should share similar process and end-use property characteristics with conventional PVC copolymers without adversely affecting thermal stability. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1603–1612, 1997     

Studies of crosslinked styrene–alkyl acrylate copolymers for oil absorbency application. I. Synthesis and characterization

The prepolymers for a novel oil absorbent were synthesized by copolymerizing styrene with 2‐ethylhexyl acrylate (EHA), lauryl acrylate (LA), lauryl methacrylate (LMA), and stearyl acrylate (SA). Suspension polymerization was carried out using benzoyl peroxide (BPO) as an initiator with a varying monomer feed ratio, and the copolymers were characterized by FTIR, ¹H‐NMR, DSC, and a solubility test. The copolymers were random copolymers with a single phase, and their compositions were similar to those in the monomer feed. The T_g of the copolymer could be controlled by varying the styrene/acrylate ratio. Acrylates introduced the crosslinking to linear polymers as a side reaction. Crosslinked copolymers were synthesized by adding divinylbenzene (DVB) as a crosslinking agent. At a low degree of crosslinking (0.5 wt % DVB), the T_g of the crosslinked copolymers was lower than or similar to that of the uncrosslinked ones. At a high degree of crosslinking, the T_g increased with increasing crosslinking density. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 903–913, 2000     

Synthesis and characterization of liquid crystalline polymers from p-hydroxybenzoic acid,poly(ethylene terephthalate), and third monomers

Eight new p-hydroxybenzoic acid (PHB) and poly(ethylene terephthalate) (PET) copolymers containing vanillic acid (VA), p-aminobenzoic acid, m-hydroxybenzoic acid, hydroquinone/terephthalic acid (TPA), bisphenol A/TPA, 1,5-naphthalenediol/TPA, 2,7-naphthalenediol/TPA, and 1,4-dihydroxyanthraquinone/TPA as eight third monomers with a variety of structural features were synthesized by melted-state copolycondensation and were characterized through a thermal analyzer, proton nuclear magnetic resonance, wide-angle X-ray diffraction (WAXD), and a scanning electron microscope (SEM). The experimental results show that PHB/PET/VA copolymers exhibit a faster polycondensation rate, lower melting temperature, and higher thermostability than do the other seven copolymers and third monomer-free PHB/PET polymers. The as-spun fibers derived from the PHB/PET/VA copolymers with different VA contents show tensile strengths, Young's moduli, and break elongations of 0.6–1.5 GPa, 28–67 GPa, and 7–9%, respectively. A highly oriented fibrillar structure in the PHB/PET/VA copolymer fibers was observed using WAXD and SEM. The most effective third monomer of the eight third monomers for an enhancing polycondensation rate and molecular weight of the PHB/PET polymers and for improving their thermal and mechanical properties is found to be vanillic acid (VA). © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2129–2138, 1997     

Grafting of oligopeptide on poly(aminostyrene)s and characterization of the polymers

Graft copolymers that have oligopeptides (OP) as graft molecules were prepared through the coupling reaction of the carboxylic acids of OP with the amino groups of poly(aminostyrene)s (PAS). The three OPs are Boc‐Gly, Z‐Gly‐Pro, and Z‐Gly‐Pro‐Leu‐Gly‐Pro, where Boc and Z are, respectively, the t‐butyloxycarbonyl group and benzyloxycarbonyl group as protective groups on nitrogen. The two PASs are poly(4‐vinylphenylamine) and poly(N‐isopropyl‐4‐vinylbenzylamine). These polymers that have narrow molecular weight distributions were prepared via anionic living polymerization. The coupling reaction to form the peptide bonds was mediated by dicyclohexylcarbodiimide in a mixed solvent of N,N′‐dimethylformamide and methyl chloride. The degree of grafting (DOG) on PAS was determined from the ¹H‐NMR spectrum. The dependence of the reaction time (0–8 h) on the DOG, the dependence of the reaction temperature (0–45°C) on the DOG, and the dependence of the molar ratio of OP to the amino group of PAS (1–4 times) on the DOG were studied. By alternating the reaction time and the molar ratio, the DOG values of PAS could be controlled in the range from 0 to 100%. DOG seems to be independent of the molecular weight of OP and the degree of basicity of PAS. The contact angle of the resultant graft copolymers was measured and the preliminary nonthrombogenic test was also performed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1558–1567, 2000     

Aminolysis reaction of poly(N-4-methylphenylitaconimide) and its graft copolymerization

Polyitaconimide and copolymers of itaconimide were transformed to macromolecules having diamido pendent groups via an aminolysis reaction. The polymers obtained were cast into films, which were then graft copolymerized with acrylamide (AAM) using ceric ion as an initiator. Radical homopolymerization and copolymerization of N-4-methylphenylitaconimide with methyl acrylate or ethyl acrylate were carried out at 60°C in benzene; high molecular weight polymer and copolymers (M?_n = 10⁴–10⁵) were obtained. The resulting polymer and copolymers were reacted with n-butylamine in order to produce polymers possessing a pendent 4-tolylcarbamoyl group (4-CH₃C₆H₄NHCO-), which can significantly promote the acrylamide (AAM) graft copolymerization initiated with ceric ion. Transparent films of the polymers were graft copolymerized with AAM in the presence of ceric ion at 45°C. The formation of graft polymers was verified by water absorption percentage, XPS and SEM.     

Novel ultrasonic process for in‐situ copolymer formation and compatibilization of immiscible polymers

In‐situ copolymer formation and compatibilization of immiscible polymers in blends were discovered to occur during ultrasonic‐assisted extrusion in the melt state under high pressures. Residence times were of the order of seconds. The mechanical performance of plastic/rubber and rubber/rubber blends subjected to ultrasonic treatment was significantly enhanced compared to those of identical blends not subjected to ultrasonic treatment and having similar phase morphologies. The appearance of a high molecular weight tail in the rubber/rubber blends, stabilization of phase morphology in the melt state, the presence of a transition interface nanolayer and a decrease in the amount of extractable components in the plastic/rubber blends after ultrasonic‐assisted extrusion point towards the occurrence of in‐situ copolymer formation at the interfaces.     

Synthesis of triblock and random copolymers of 4-acetoxystyrene and styrene by living atom transfer radical polymerization

Triblock copolymers containing polystyrene (PSt) and poly(4-acetoxystyrene) (PAcOSt) segments have been prepared by atom transfer radical polymerization (ATRP). In the first step one of the two monomers was polymerized in bulk using the initiating system α,α′-dibromo-p-xylene/CuBr/2,2′-bipyridine (1/1/3). Subsequently the resulting telechelic polymers with active bromo end group structures were used as macroinitiators for the polymerization of the second monomer under ATRP conditions. This process gave PAcOSt-PSt-PAcOSt and PSt-PAcOSt-PSt triblock copolymers with predetermined molecular weights and narrow molecular weight distributions. Polymerization of a mixture of equal molar amounts of the two monomers yielded a random copolymer with narrow molecular weight distribution. Received: 25 June 1997/Revised: 25 August 1997/Accepted: 8 September 1997     

Gamma‐irradiated metallocenic polyethylene and ethylene‐1‐hexene copolymers

The aim of this work is to present a detailed study of the changes introduced by gamma radiation on several metallocenic polyethylene copolymers. Therefore, metallocenic polyethylene and copolymers with 3.3, 9.2, and 16.1 mol % of hexene comonomer content were synthesized and irradiated with ⁶⁰Co gamma radiation under vacuum at room temperature with radiation doses ranging from 0 to 100 kGy. Size Exclusion Chromatography data show that crosslinking reactions predominate over scission, even for the copolymer with the highest tertiary carbon content. Over a certain critical dose, which depends on the molecular weight and molecular structure of the initial polymer, an insoluble gel forms. The irradiated polymers also exhibit complex rheological behavior with increasing melt viscosity and elasticity, consistent with long chain branching and/or crosslinking. FTIR confirms depletion of terminal vinyl groups and increase of trans unsaturations with dose. The rate at which these two reactions evolve seems to depend on the comonomer content of the irradiated copolymers. Differential scanning calorimetry and Raman spectroscopy analyzes indicate less crystallinity and thicker interphases in irradiated materials. A mathematical model, which accounts for scission and crosslinking reactions, fitted well the evolution with radiation dose of the measured molecular weight data. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermal degradation of polymers. XIV. Thermal analysis studies in air on homopolymers of m-N,N-dimethylaminostyrene and p-N,N-diethylaminostyrene and their copolymers with styrene

Homopolymers of m-N,N-diethylaminostyrene and p-N,N-diethylaminostyrene and their copolymers with styrene have been subjected to thermal analysis studies in air. Molecular weight and copolymer composition have been shown to influence the stability of the polymers and the shape of the TG and DSC curves in the case of polymers containing m-N,N-dimethylaminostyrene. Polymers containing p-N,N-diethylaminostyrene show TG and DSC curves essentially independent of molecular weight and copolymer composition. The behavior of the two systems is discussed in terms of the antioxidant effect of the chain-bound N,N-dialkylamino substituents and their secondary reactions.     

Synthesis and characterization of four‐arm star‐shaped polymers and copolymers

Four‐arm star‐shaped polymers and copolymers were obtained by transition metal‐catalyzed atom‐transfer radical polymerization (ATRP). The polymers were characterized by FTIR and ¹H‐NMR spectroscopy. Gel permeation chromatography results indicated the formation of polystyrene and polystyrene‐block‐poly(methyl methacrylate) (PS‐b‐PMMA) arms with controlled molecular weights. In dilute solution, the linear polymers had higher inherent viscosities than star‐shaped ones. Thermogravimetric analysis showed a similar degradation mechanism for linear and star‐shaped polymers. Differential scanning calorimetry indicated the successful formation of diblock star‐shaped copolymers. Copyright © 2006 Society of Chemical Industry     

Preparation and characterization of novel crosslinked poly[glycidyl methacrylate–poly(ethylene glycol) methyl ether methacrylate] as gel polymer electrolytes

In this study, glycidyl methacrylate was copolymerized with poly(ethylene glycol) methyl ether methacrylate to obtain a copolymer {poly[glycidyl methacrylate–poly(ethylene glycol) methyl ether methacrylate] [P(GMA–PEGMA)]}, which was crosslinked with α,ω‐diamino poly(propylene oxide) (Jeffamine) at various weight ratios and molecular weights to form novel gel polymer electrolytes (GPEs). The crosslinked copolymers were characterized by Fourier transform infrared spectroscopy and thermal analysis. The crosslinked polymers were amorphous in the pristine state and became crystallized after they were doped with lithium electrolyte. Furthermore, the crosslinking degree of the crosslinked polymers increased with increasing weight ratio of Jeffamine, and both the swelling properties and mechanical behaviors of the crosslinked polymers were heavily affected by the weight ratio and molecular weight of Jeffamine. The ionic conductivity (σ) of the GPEs from the crosslinked copolymers was determined by alternating‐current impedance spectroscopy. A higher molecular weight and increased weight ratio of Jeffamine resulted in a higher σ. The GPE based on P(GMA–PEGMA) crosslinked with an equal weight of Jeffamine D2000 exhibited the highest σ of 8.29 × 10⁻⁴ S/cm at 25°C and had a moderate mechanical strength. These crosslinked copolymers could be potential candidates for the construction of rechargeable lithium batteries. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of superabsorbent polymers by crosslinking acrylic acid and acrylamide copolymers

High water-absorbent copolymers comprising acrylic acid (AA) and acrylamide (AM) were prepared in the presence of a crosslinking agent, monofunctional aldehyde, by a solution polymerization technique using a redox initiation system. Such copolymers have very high water absorbency and absorbing kinetics to the distilled water. The copolymer formed which absorbed about 900 g water/g dry copolymer was used to study the influence of sodium chloride on the absorption capacity at 24°C. The swelling of this copolymer was studied in alcohol/water mixtures of increasing alcohol content at 294, 304, and 314 K. The main transition for ethanol/water and methanol/water mixtures is a rapid decrease of the retention capacity of the copolymer at 50–60 vol % ethanol and 55–65 vol % methanol, respectively. Swelling in distilled water at different temperatures (T) and the effect of solvent composition were also studied. Among the variables examined were initiator concentration, polymerization temperature, and amount of AM in the copolymer. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1345–1353, 1997